Recovery of rare earth elements (Lu, Y) by adsorption using functionalized SBA-15 and MIL-101 (Cr)

Due to increasing application in the green energy sector, rare earth elements (REEs) have become a precious commodity in the international market. The REEs, Yttrium (Y) and Lutetium (Lu) are used as catalysts in wide array of industries. SBA-15 modified with 1,4-phthaloyl diamido-propyltriethoxysilane (1,4-PA-APTES) ligands; and chromium based metal organic frameworks (MOF) modified with PMIDA (MIL-101-PMIDA) were prepared in this study as potential adsorbents for recovery of these elements. The adsorption capacities for Lu and Y on virgin SBA-15 were negligible. After modification of SBA-15, the Langmuir adsorption capacities for Lu and Y significantly increased to 17.0 and 17.9 mg/L, respectively. The Langmuir adsorption capacities of Lu and Y on PMIDA modified MIL-101 (MIL-101-PMIDA) were 63.4 and 25.3 mg/g, respectively. Higher adsorption capacities of the MOF are due to its higher surface area (1050 m(2)/g) and beneficial functional groups such as phosphonic group present on the adsorbent surface and it attributes to rapider REE adsorption on MIL-101-PMIDA than on1,4-PA-SBA. Lu adsorption capacity was 2.5 times higher than Y due to its superior ion-exchange capability with grafted phosphonic groups. Both adsorbents retained over 90% of adsorption capacity after 5 adsorption/desorption cycles which demonstrate the high structural stability of the materials.

Automated summary

Due to the increasing application of rare earth elements in the green energy sector, they have become precious commodities in the international market. Modified SBA-15 and chromium-based MOFs show high adsorption capacities for Lu and Y, with the MOF demonstrating superior ion-exchange capabilities. The adsorbents display high structural stability, retaining over 90% of adsorption capacity after multiple cycles.